Sofa



FIG. 1 is a perspective view of a sofa showing my new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a top plan view thereof; and,

FIG. 5 is a right side view thereof.

The rear of the sofa forms no part of the claimed design. 

The ornamental design for a sofa, as shown and described. 